n: a crusty, usually white substance that appears on different things(clothes, bed sheets, etc.) mostly because of sloppy ejaculation.
v: to shoot someone or something with the substance in its goopy state, before crusting. ejaculation of anything that can launch a goopy fluid.

1. Fuckin' skack is all over my fuckin' pants. Fuck.
2. Samantha did not know that i skacked on her back in the middle of math class.